Reliability modeling and analysis of low power portable direct methanol fuel cell

This thesis presents a detailed reliability assessment of low power portable DMFC systems. At first, system configuration and model are developed to calculate the reliability of the DMFC system. A sensitivity analysis on the reliability of DMFC is also used to determine the components that are critical to ensure the reliability of the system. For reliability assessment and sensitivity analysis, a reliability block diagram (RBD) is used to develop the analytical model of the DMFC system. A state space model is used to formulate the state-space Markov model (MM), which is a very effective technique for calculating repairable system reliability and availability. Since most of the systems and associated components spend their lifetime in the steady state period, this research is focused mainly on the steady state operational period. The failure time and repair time for repairable DMFC systems are fitted with a homogeneous Poisson process (HPP) and exponential distribution. The parameters of these models can be considered as constant for the steady state period. These constant parameters are used in the MM transition matrix to calculate the availability and reliability of low power portable DMFC systems. Simulation results calculated based on the state space model for 5000 hours indicate that the system reliability is 90.51% and steady state system availability is 99.94%.